One electrophotographic image forming apparatus known in the art is a color printer that includes a main casing, a drum unit that can be mounted in and removed from the main casing along a front-rear direction, and a plurality of developer cartridges that are detachably mounted in the drum unit. The drum unit is provided with a plurality of photosensitive drums corresponding to a plurality of colors (yellow, magenta, cyan, and black, for example). The photosensitive drums are arranged parallel to one another and juxtaposed in the front-rear direction. The plurality of developer cartridges corresponds to the plurality of photosensitive drums. Each developer cartridge includes a developing roller for supplying toner to the corresponding photosensitive drum.
This type of color printer may also have another well-known structure that brings the developing roller of each developer cartridge into contact with the corresponding photosensitive drum in order to supply toner to the photosensitive drum during an image-forming operation, and to separate the developing roller from the photosensitive drum in order to prevent the supply of toner when not forming images.
One of these color printers that has been proposed is a color laser printer that includes separating/pressing mechanisms for pressing the corresponding developing rollers against or separating the developing rollers from the corresponding photosensitive drums. The separating/pressing mechanisms are provided in the main casing, and are also provided one on each axial end of the photosensitive drums when the drum unit is mounted in the main casing.
In this type of color laser printer, the developer cartridges are mounted in and removed from the drum unit in a substantially vertical direction while the drum unit is withdrawn from the main casing.
Further, another electrophotographic image forming apparatus known in the art is provided with a casing; a plurality of process cartridges arranged parallel to each other and juxtaposed in a prescribed direction inside the casing, each process cartridge integrally including a photosensitive drum and a toner-accommodating unit; and a plurality of LED units provided in one-to-one correspondence with the plurality of photosensitive drums for exposing the photosensitive drums.
One such image forming apparatus that has been proposed is a color multifunction peripheral whose casing is provided with a support frame, for example, that can be mounted in and pulled out of the casing in a front-rear direction. The support frame integrally supports the plurality of process cartridges. The support frame is provided with support arms for supporting the LED units between toner-accommodating units of neighboring process cartridges.
In the conventional color multifunction peripheral described above, the process cartridges are mounted in and removed from the support frame in a substantially vertical direction in a state where the support frame has been withdrawn from the casing.